The objective of the proposed research is to study the pathophysiology of cystic fibrosis (CF) in a cellular model system of isolated rat parotid acinar cells exhibiting pharmacologically induced dysfunction. Using methods for the isolation of morphologically and functionally intact human parotid acinar cells from patients with CF, the following were observed: (a) acinar cell enlargement; (b) altered cationic composition of the cells; (c) altered transmembrane fluxes of Na ion and Ca2 ion; (d) depressed stimulus-secretion coupling during activation of the muscarinic cholinergic receptors; and (e) hyperactivity of the stimulus-secretion coupling during activation of the beta adrenergic receptors. Because of the infrequent availability of parotid acinar cells from patients with CF and the unavailability of a natural animal model for this disease, cellular dysfunction of the parotid was induced pharmacologically by the chronic administration of either DL-isoproterenol or reserpine to the albino rat. Preliminary studies indicated that the acinar cells from these parotids exhibited similar, if not identical, dysfunction to that observed in the cells from patients with CF. It is proposed to study in detail the dysfunction of these cells in order to develop better understanding of the cellular pathophysiology of CF as follows: (a) cell morphology; (b) cell composition (Na ion, K ion, Ca2 ion, ATP); (c) transmembrane fluxes of Na ion, K ion, and Ca2 ion; (d) stimulus-secretion coupling during activation of muscarinic cholinergic receptors; and (e) stimulus-secretion coupling during beta-adrenergic receptor activation. In addition, because preliminary studies have implicated abnormal handling of Ca2 ion as a common denominator of the observed dysfunction in parotid acinar cells from CF patients and in the above cellular model systems for CF, the effects of experimental Ca2 ion overloading or Ca2 ion depletion will also be studied in isolated rat parotid acinar cells. It is expected that these studies will help elucidate the cellular pathophysiology of CF, which may lead to better methods of pharmacological intervention in the treatment of this disease.